Problem 1P In lab, Will burns a 0.6-g peanut beneath 50 g of water, which increases in temperature from 22°C to 50°C. The amount of heat absorbed by the water can be found with the equation ?Q? = cm? ? ?T,? where ?Q? is the amount of heat, ?c? the specific heat of water, ?m? the mass of water, and ? ?T? the change in the water’s temperature. a. Assuming that 40% of the heat released makes its way to the water, show that the food value of the peanut is 3500 calories, or 3.5 Calories. b. What is the food value in calories per gram? In Calories per gram?
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Table of Contents
Textbook Solutions for Conceptual Physics
Question
In lab you submerge 100 g of 40°C iron nails in 100 g of 20°C water (the specific heat of iron is 0.12 cal/g°C.) (a) Equate the heat gained by the water to the heat lost by the nails and show that the final temperature of the water becomes 22.1°C. (b) Your lab partner is surprised by the result and says that since the masses of iron and water are equal, the final water temperature should lie closer to 30°C, half-way between. What is your explanation?
Solution
Solution 5P 0 (a) Let the final temperature be x C Specific heat of water is = 1 cal/g C0 Initial temperature of water = 20 C 0 Mass of water = 100 g Therefore, heat gained by water= mass × specific heat × change in temperature 0 0 = 100 g × 1 cal/g C × (x 20) C = 100(x 20) cal …..(1) Mass of the nails = 100 g Specific heat of iron = 0.12 cal/g C0 Initial temperature of the nail
full solution
In lab you submerge 100 g of 40°C iron nails in 100 g of
Chapter 16 textbook questions
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Chapter 16: Problem 1 Conceptual Physics 12
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Chapter 16: Problem 1 Conceptual Physics 12
Problem 1E On a cold day, why does a metal doorknob feel colder than the wooden door?
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Chapter 16: Problem 1 Conceptual Physics 12
Problem 1RQ What is the role of “loose” electrons in heat conductors?
Read more -
Chapter 16: Problem 56 Conceptual Physics 12
Problem 56E Make up a multiple-choice question that would test a classmate’s understanding of the distinction between conduction and convection. Make another in which the term ?radiation? is the correct answer.
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Chapter 16: Problem 2 Conceptual Physics 12
Problem 2E What is the explanation for feather beds being warm?
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Chapter 16: Problem 2 Conceptual Physics 12
Problem 2P Radioactive decay of granite and other rocks in Earth’s interior provides sufficient energy to keep the interior molten, to heat lava, and to provide warmth to natural hot springs. This is due to the average release of about 0.03 J per kilogram each year. Show that a 500°C increase in temperature for a thermally insulated chunk of granite takes about 13.3 million years. (Assume that the specific heat capacity ?c? of granite is 800 J/kg·C°. Use the equation Q ? ? =? m??? ?)
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Chapter 16: Problem 2 Conceptual Physics 12
Problem 2RQ If you touch the metal sides inside of an oven with a bare hand, you’re in trouble. But hold your hand briefly in the oven air and you’re okay. What does this tell you about the relative conductivities of metal and air?
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Chapter 16: Problem 3 Conceptual Physics 12
Problem 3E Wrap a fur coat around a thermometer. Will the temperature rise?
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Chapter 16: Problem 3 Conceptual Physics 12
Problem 3P In a 25°C room, hot coffee in a vacuum flask cools from 75°C to 50°C in 8 hours. Explain why you predict that its temperature after another 8 hours will be 37.5°C.
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Chapter 16: Problem 3 Conceptual Physics 12
Problem 3RQ Explain why a firewalker can step quickly without harm on red-hot coals with bare feet.
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Chapter 16: Problem 4 Conceptual Physics 12
Problem 4E If 70°F air feels warm and comfortable to us, why does 70°F water feel cool when we swim in it?
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Chapter 16: Problem 4 Conceptual Physics 12
Problem 4P At a certain location, the solar power per unit area reaching Earth’s surface is 200 W/m2, averaged over a 24-hour day. If the average power requirement in your home is 3 kW and you can convert solar power to electric power with 10% efficiency, how large a collector area will you need to meet all your household energy requirements from solar energy? (Will a collector fit in your yard or on your roof?)
Read more -
Chapter 16: Problem 4 Conceptual Physics 12
Problem 4RQ Why are such materials as wood, fur, feathers, and even snow good insulators?
Read more -
Chapter 16: Problem 5 Conceptual Physics 12
Problem 5E At what common temperature will a block of wood and a block of metal both feel neither hot nor cold to the touch?
Read more -
Chapter 16: Problem 5 Conceptual Physics 12
Problem 5P In lab you submerge 100 g of 40°C iron nails in 100 g of 20°C water (the specific heat of iron is 0.12 cal/g°C.) (a) Equate the heat gained by the water to the heat lost by the nails and show that the final temperature of the water becomes 22.1°C. (b) Your lab partner is surprised by the result and says that since the masses of iron and water are equal, the final water temperature should lie closer to 30°C, half-way between. What is your explanation?
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Chapter 16: Problem 5 Conceptual Physics 12
Problem 5RQ Does a good insulator prevent heat from escaping, or does it simply slow its passage?
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Chapter 16: Problem 6 Conceptual Physics 12
Problem 6E If you hold one end of a piece of metal against a piece of ice, the end in your hand soon becomes cold. Does cold flow from the ice to your hand? Explain.
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Chapter 16: Problem 6 Conceptual Physics 12
Problem 6RQ What happens to the volume of air as it rises? What happens to its temperature?
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Chapter 16: Problem 7 Conceptual Physics 12
Problem 7E What is the purpose of a layer of copper or aluminum on the bottom of stainless steel cookware?
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Chapter 16: Problem 7 Conceptual Physics 12
Problem 7RQ When an air molecule is hit by an approaching faster-moving molecule, does its rebound speed increase or decrease? How about when it hits a receding molecule?
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Chapter 16: Problem 8 Conceptual Physics 12
Problem 8E In terms of physics, why do restaurants serve baked potatoes wrapped in aluminum foil?
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Chapter 16: Problem 8 Conceptual Physics 12
Problem 8RQ How are the speeds of molecules of air affected when the air is compressed by the action of a tire pump?
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Chapter 16: Problem 9 Conceptual Physics 12
Problem 9E Wood is a better insulator than glass, yet fiberglass is commonly used as an insulator in wooden buildings. Explain.
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Chapter 16: Problem 9 Conceptual Physics 12
Problem 9RQ How are the speeds of molecules of air affected when the air rapidly expands?
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Chapter 16: Problem 10 Conceptual Physics 12
Problem 10E Many tongues have been injured by licking a piece of metal on a very cold day. Why would no harm result if a clean piece of wood were licked on the same day?
Read more -
Chapter 16: Problem 10 Conceptual Physics 12
Why is Millie’s hand not burned when she holds it above the escape valve of the pressure cooker?
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Chapter 16: Problem 11 Conceptual Physics 12
Problem 11E Visit a snow-covered cemetery and note that the snow does not slope upward against the grave-stones. Instead, it forms depressions, as shown. Can you think of a reason for this?
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Chapter 16: Problem 12 Conceptual Physics 12
Problem 12E Why are mittens warmer than gloves on a cold day?
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Chapter 16: Problem 11 Conceptual Physics 12
Problem 11RQ Why does the direction of coastal winds change from day to night?
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Chapter 16: Problem 13 Conceptual Physics 12
Problem 13E If you were caught in freezing weather with only your own body heat as a source, would you be warmer in an Arctic igloo or in a wooden shack? Defend your answer.
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Chapter 16: Problem 13 Conceptual Physics 12
Problem 13RQ Relatively speaking, do high-frequency waves have long wavelengths or short wavelengths?
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Chapter 16: Problem 14 Conceptual Physics 12
Problem 14E Wood conducts heat very poorly—it has a very low conductivity. Does wood still have a low conductivity if it is hot? Could you quickly and safely grasp the wooden handle of a pan from a hot oven with your bare hand? Although the pan handle is hot, is much heat conducted from it to your hand if grasped briefly? Why would it be a poor idea to do the same with an iron handle? Explain.
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Chapter 16: Problem 14 Conceptual Physics 12
How does the frequency of radiant energy relate to the absolute temperature of the radiating source?
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Chapter 16: Problem 15 Conceptual Physics 12
Problem 15E Does wood have a low conductivity if it is very hot—that is, in the stage of smoldering, red-hot coals? Could you safely walk across a bed of red-hot wooden coals with bare feet? Although the coals are hot, does much heat conduct from them to your feet if you step quickly? Could you do the same on red-hot iron coals? Explain. (?Caution:? Coals can stick to your feet, so—OUCH!—don’t try it!)
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Chapter 16: Problem 16 Conceptual Physics 12
Problem 16E Is it possible for heat to flow between two objects with the same internal energy? Can heat flow from an object with less internal energy to one with more internal energy? Defend your answers.
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Chapter 16: Problem 16 Conceptual Physics 12
Problem 16RQ Cite a primary difference between waves of solar radiation and waves of terrestrial radiation.
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Chapter 16: Problem 17 Conceptual Physics 12
Problem 17E When two cups of hot chocolate, one at 50°C and the other at 60°C, are poured into a bowl, why will the temperature of the mixture be between 50°C and 60°C?
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Chapter 16: Problem 17 Conceptual Physics 12
Problem 17RQ Since all objects emit energy to their surroundings, why don’t the temperatures of all objects continuously decrease?
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Chapter 16: Problem 18 Conceptual Physics 12
Problem 18E Why is it incorrect to say that, when a hot object warms a cold object, temperature flows between them?
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Chapter 16: Problem 18 Conceptual Physics 12
Problem 18RQ What determines whether an object is a net absorber or a net emitter of radiant energy at a given time?
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Chapter 16: Problem 19 Conceptual Physics 12
Why is it incorrect to say that, when a hot object warms a cold one, the increase in temperature of the cold one is equal to the decrease in temperature of the hot one? When is this statement correct?
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Chapter 16: Problem 19 Conceptual Physics 12
Problem 19RQ Which will normally warm faster—a black pot of cold water or a silvered pot of cold water? Explain.
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Chapter 16: Problem 20 Conceptual Physics 12
Problem 20E A friend says that the molecules in a mixture of gas in thermal equilibrium have the same average kinetic energy. Do you agree or disagree? Explain.
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Chapter 16: Problem 20 Conceptual Physics 12
Problem 20RQ Can an object be both a good absorber and a good reflector at the same time? Why, or why not?
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Chapter 16: Problem 21 Conceptual Physics 12
Problem 21E Your friend states that the average speed of all hydrogen and nitrogen molecules in a gas is the same. Do you agree or disagree, and why?
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Chapter 16: Problem 21 Conceptual Physics 12
Calculate the osmotic pressure of a solution containing \(24.6 \mathrm{~g}\) of glycerin \(\left(\mathrm{C}_3 \mathrm{H}_8 \mathrm{O}_3\right)\) in \(250.0 \mathrm{~mL}\) of solution at \(298 \mathrm{~K}\).
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Chapter 16: Problem 22 Conceptual Physics 12
Problem 22E Why would you not expect all the molecules of air in your room to have the same average speed?
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Chapter 16: Problem 22 Conceptual Physics 12
Problem 22RQ What happens to the temperature of something that radiates energy without absorbing the same amount in return?
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Chapter 16: Problem 24 Conceptual Physics 12
Problem 24E One container is filled with argon gas and the other with krypton gas. If both gases have the same temperature, in which container are the atoms moving faster? Why?
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Chapter 16: Problem 25 Conceptual Physics 12
Problem 25E Which atoms, on average, move slower in a mixture, U-238 or U-235? How would this affect diffusion through a porous membrane of otherwise identical gases made from these isotopes?
Read more -
Chapter 16: Problem 24 Conceptual Physics 12
Problem 24RQ Which will undergo the greater rate of cooling—a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?
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Chapter 16: Problem 25 Conceptual Physics 12
Problem 25RQ Does Newton’s law of cooling apply to warming as well as to cooling?
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Chapter 16: Problem 23 Conceptual Physics 12
Problem 23RQ An object radiating energy at night is in contact with the relatively warm Earth. How does its conductivity affect whether or not it becomes appreciably colder than the air?
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Chapter 16: Problem 23 Conceptual Physics 12
Problem 23E In a mixture of hydrogen and oxygen gases at the same temperature, which molecules move faster? Why?
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Chapter 16: Problem 26 Conceptual Physics 12
Solid uranium can be converted chemically to uranium fluoride, \(\mathrm{UF}_{6}\) , which can be cooked up into a dense vapor that diffuses through a porous barrier. Which is likely to diffuse at a greater rate: a gas with isotope U-235 or U-238?
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Chapter 16: Problem 26 Conceptual Physics 12
Problem 26RQ What would be the consequence of completely eliminating the greenhouse effect?
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Chapter 16: Problem 27 Conceptual Physics 12
Problem 27RQ In what way does glass act like a one-way valve for a conventional greenhouse? Does the atmosphere play the same role?
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Chapter 16: Problem 27 Conceptual Physics 12
What would be the consequence of completely eliminating the greenhouse effect?
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Chapter 16: Problem 28 Conceptual Physics 12
Problem 28E In a still room, smoke from a candle will sometimes rise only so far, not reaching the ceiling. Explain why.
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Chapter 16: Problem 28 Conceptual Physics 12
Problem 28RQ How much radiant energy from the Sun, on average, reaches each square meter at the top of Earth’s atmosphere each second?
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Chapter 16: Problem 29 Conceptual Physics 12
Soaring birds and glider pilots can remain aloft for hours without expending power. How do they do it?
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Chapter 16: Problem 29 Conceptual Physics 12
Problem 29RQ What is the function of a photovoltaic cell?
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Chapter 16: Problem 30 Conceptual Physics 12
Problem 30RQ Cite three ways in which a Thermos bottle inhibits heat transfer.
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Chapter 16: Problem 30 Conceptual Physics 12
Problem 30E Why does helium, released into the atmosphere, eventually disappear into space?
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Chapter 16: Problem 32 Conceptual Physics 12
Problem 32E Release a single molecule in an evacuated region and it will fall as fast as, and no differently from, a baseball released in the same region. Explain.
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Chapter 16: Problem 31 Conceptual Physics 12
Problem 31E Ice cubes float in a glass of iced tea. Why would cooling be less if the cubes were instead on the bottom of the drink?
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Chapter 16: Problem 34 Conceptual Physics 12
Problem 34E What does the high specific heat of water have to do with convection currents in the air at the seashore?
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Chapter 16: Problem 35 Conceptual Physics 12
Problem 35E If we warm a volume of air, it expands. Does it then follow that if we expand a volume of air, it warms? Explain.
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Chapter 16: Problem 36 Conceptual Physics 12
Problem 36E Ceiling fans can make you feel cooler in a warm room. Do ceiling fans reduce room temperature?
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Chapter 16: Problem 39 Conceptual Physics 12
Problem 39E In which form of heat transfer is a medium not required?
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Chapter 16: Problem 38 Conceptual Physics 12
Problem 38E A snow-making machine used for ski areas blows a mixture of compressed air and water through a nozzle. The temperature of the mixture may initially be well above the freezing temperature of water, yet crystals of snow are formed as the mixture is ejected from the nozzle. Explain how this happens.
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Chapter 16: Problem 40 Conceptual Physics 12
Problem 40E Why does a good ?emitter? of heat radiation appear black at room temperature?
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Chapter 16: Problem 41 Conceptual Physics 12
Problem 41E Since energy is radiated by all objects, why can’t we see them in the dark?
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Chapter 16: Problem 42 Conceptual Physics 12
Problem 42E A number of bodies at different temperatures placed in a closed room share radiant energy and ultimately reach a common temperature. Would this thermal equilibrium be possible if good absorbers were poor emitters and poor absorbers were good emitters? Explain.
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Chapter 16: Problem 43 Conceptual Physics 12
Problem 43E From the rules that a good absorber of radiation is a good radiator and a good reflector is a poor absorber, state a rule relating the reflecting and radiating properties of a surface.
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Chapter 16: Problem 44 Conceptual Physics 12
Problem 44E The heat of volcanoes and natural hot springs comes from trace amounts of radioactive minerals in common rock in Earth’s interior. Why isn’t the same kind of rock at Earth’s surface warm to the touch?
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Chapter 16: Problem 45 Conceptual Physics 12
Problem 45E Even though metal is a good conductor, frost can be seen on parked cars in the early morning even when the air temperature is above freezing. Provide an explanation.
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Chapter 16: Problem 46 Conceptual Physics 12
Problem 46E When there is morning frost on the grass in an open park, why is frost unlikely to be found on the ground directly beneath park benches?
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Chapter 16: Problem 47 Conceptual Physics 12
Why is whitewash sometimes applied to the glass of florists’ greenhouses in the summer?
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Chapter 16: Problem 48 Conceptual Physics 12
Problem 48E On a very cold sunny day, you wear a black coat and a transparent plastic coat. Which coat should be worn on the outside for maximum warmth?
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Chapter 16: Problem 49 Conceptual Physics 12
Problem 49E If the composition of the upper atmosphere were changed so that it permitted a greater amount of terrestrial radiation to escape, what effect would this have on Earth’s climate?
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Chapter 16: Problem 50 Conceptual Physics 12
Problem 50E Is it important to convert temperatures to the Kelvin scale when we use Newton’s law of cooling? Why or why not?
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Chapter 16: Problem 51 Conceptual Physics 12
Problem 51E Why is the insulation in an attic commonly thicker than the insulation in the walls of a house?
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Chapter 16: Problem 52 Conceptual Physics 12
Problem 52E Suppose that, at a restaurant, you are served coffee before you are ready to drink it. In order that it be hottest when you are ready for it, should you add cream to the coffee right away or wait until you are ready to drink it?
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Chapter 16: Problem 54 Conceptual Physics 12
Problem 54E If you wish to save fuel and you’re going to leave your cool house for a half hour or so on a very hot day, should you turn your air-conditioning thermostat up a bit, turn it off altogether, or let it remain at the room temperature you desire?
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Chapter 16: Problem 53 Conceptual Physics 12
Problem 53E If you wish to save fuel and you’re going to leave your warm house for a half hour or so on a very cold day, should you turn your thermostat down a few degrees, turn it off altogether, or let it remain at the room temperature you desire?
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Chapter 16: Problem 55 Conceptual Physics 12
Problem 55E As more energy from fossil fuels and other fuels is released on Earth, the overall temperature of Earth tends to rise. How does temperature equilibrium explain why Earth’s temperature cannot rise indefinitely?
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Chapter : Problem 1 Conceptual Physics 12
What is the role of “loose” electrons in heat conductors?
Read more -
Chapter : Problem 2 Conceptual Physics 12
If you touch the metal sides in an oven with your bare hand, you’re in trouble. But hold your hand briefly in the oven air and you’re okay. What does this tell you about the relative conductivities of metal and air?
Read more -
Chapter : Problem 3 Conceptual Physics 12
Explain why a firewalker can step quickly without harm on red-hot coals with bare feet.
Read more -
Chapter : Problem 4 Conceptual Physics 12
Why are materials such as wood, fur, feathers, and even snow good insulators?
Read more -
Chapter : Problem 5 Conceptual Physics 12
Does a good insulator prevent heat from escaping or slow its passage?
Read more -
Chapter : Problem 6 Conceptual Physics 12
What happens to the volume of air as it rises? What happens to its temperature?
Read more -
Chapter : Problem 7 Conceptual Physics 12
When an air molecule is hit by an approaching faster-moving molecule, does its rebound speed increase or decrease? How about when it hits a receding molecule?
Read more -
Chapter : Problem 8 Conceptual Physics 12
How are the speeds of molecules of air affected when the air is compressed by the action of a tire pump?
Read more -
Chapter : Problem 9 Conceptual Physics 12
How are the speeds of molecules of air affected as they separate from one another when escaping from the nozzle of a party balloon?
Read more -
Chapter : Problem 10 Conceptual Physics 12
Why isn’t Millie’s hand burned when she holds it above the escape valve of the pressure cooker (see Figure 16.8)?
Read more -
Chapter : Problem 11 Conceptual Physics 12
Why does the direction of coastal winds change from day to night?
Read more -
-
Chapter : Problem 13 Conceptual Physics 12
Relatively speaking, do high-frequency waves have long wavelengths or short wavelengths?
Read more -
Chapter : Problem 14 Conceptual Physics 12
How does the peak frequency of radiant energy relate to the absolute temperature of the radiating source?
Read more -
-
Chapter : Problem 16 Conceptual Physics 12
Cite a primary difference between waves of solar radiation and waves of terrestrial radiation.
Read more -
Chapter : Problem 17 Conceptual Physics 12
Since all objects emit energy to their surroundings, why don’t the temperatures of all objects continuously decrease?
Read more -
Chapter : Problem 18 Conceptual Physics 12
What determines whether an object is a net absorber or a net emitter of radiant energy at a given time?
Read more -
Chapter : Problem 19 Conceptual Physics 12
Which will normally warm faster: a black pot of cold water or a silvered pot of cold water? Which will cool faster?
Read more -
Chapter : Problem 20 Conceptual Physics 12
Can an object be both a good absorber and a good reflector at the same time? Why, or why not?
Read more -
-
Chapter : Problem 22 Conceptual Physics 12
What happens to the temperature of something that radiates energy without absorbing the same amount in return?
Read more -
Chapter : Problem 23 Conceptual Physics 12
An object that radiates energy at night is in contact with the relatively warm Earth. How does poor conductivity affect the object’s temperature relative to air temperature?
Read more -
Chapter : Problem 24 Conceptual Physics 12
Which will undergo the greater rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?
Read more -
Chapter : Problem 25 Conceptual Physics 12
Does Newton’s law of cooling apply to warming as well as to cooling?
Read more -
Chapter : Problem 26 Conceptual Physics 12
What would be the consequence of completely eliminating the greenhouse effect?
Read more -
Chapter : Problem 27 Conceptual Physics 12
How does glass act like a one-way valve for a conventional greenhouse? Does the atmosphere similarly act as a one-way valve?
Read more -
Chapter : Problem 29 Conceptual Physics 12
How much radiant energy from the Sun, on average, reaches each square meter at the top of Earth’s atmosphere each second?
Read more -
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Chapter : Problem 30 Conceptual Physics 12
Cite three ways in which a Thermos bottle inhibits heat transfer.
Read more -
Chapter : Problem 33 Conceptual Physics 12
Text a letter to Grandma and share your knowledge about why air temperature is cooler on clear nights and warmer on cloudy nights. With reasoned examples, convince her that all things are continuously emitting energy—and absorbing energy.
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Chapter : Problem 34 Conceptual Physics 12
Quantity of heat: \(Q=c m \Delta T\) Show that 5000 cal are required to increase the temperature of 50 g of water from \(0^{\circ} \mathrm{C}\) to \(100^{\circ} \mathrm{C}\). The specific heat capacity for water is \(1 \mathrm{cal} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\). Text Transcription: Q = cm Delta T 0^circ C 100^circ C 1 cal / g cdot ^circ C
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Chapter : Problem 35 Conceptual Physics 12
Quantity of heat: \(Q=c m \Delta T\) Calculate the quantity of heat absorbed by 20 g of water that warms from \(30^{\circ} \mathrm{C}\) to \(90^{\circ} \mathrm{C}\). Text Transcription: 30^circ C 90^circ C
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Chapter : Problem 36 Conceptual Physics 12
Radioactive decay of granite and other rocks in Earth’s interior provides sufficient energy to keep the interior molten, to heat lava, and to provide warmth to natural hot springs. This is due to the average release of about 0.03 J per kilogram each year. Show that a \(500^{\circ} \mathrm{C}\) increase in temperature for a thermally insulated chunk of granite takes about 13.3 million years. (Assume that the specific heat capacity c of granite is \(800 \ \mathrm{J} / \mathrm{kg} \cdot \mathrm{C}^{\circ}\). Use the equation \(Q=c m \Delta T\).)
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Chapter : Problem 37 Conceptual Physics 12
In a \(25^{\circ} \mathrm{C}\) room, hot coffee in a vacuum flask cools from \(75^{\circ} \mathrm{C}\) to \(50^{\circ} \mathrm{C}\) in 8 hours. Explain why your prediction is that its temperature after another 8 hours will be \(37.5^{\circ} \mathrm{C}\). Text Transcription: 25^circ C 75^circ C 50^circ C 37.5^circ C
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Chapter : Problem 38 Conceptual Physics 12
At a certain location, the solar power per unit area reaching Earth’s surface is \(200 \quad \mathrm{W} / \mathrm{m}^{2}\), averaged over a 24-hour day. If the average power requirement in your home is 3 kW and you can convert solar power to electric power with 10% efficiency, how large a collector area will you need to meet all your household energy requirements from solar energy? (Will a collector fit in your yard or on your roof?) Text Transcription: 200 W / m^2
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Chapter : Problem 39 Conceptual Physics 12
In lab you submerge 100 g of \(40^{\circ} \mathrm{C}\) iron nails in 100 g of \(20^{\circ} \mathrm{C}\) water (the specific heat of iron is \(0.11 \ \mathrm{cal} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\).) (a) Equate the heat gained by the water to the heat lost by the nails, and show that the final temperature of the water becomes \(22^{\circ} \mathrm{C}\). (b) Your lab partner is surprised by the result and says that since the masses of iron and water are equal, the final water temperature should be closer to \(30^{\circ} \mathrm{C}\), halfway between. What is your explanation?
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Chapter : Problem 40 Conceptual Physics 12
On a cold day, why does a metal doorknob feel colder than the wooden door?
Read more -
Chapter : Problem 41 Conceptual Physics 12
What is the explanation for feather beds being warm?
Read more -
Chapter : Problem 42 Conceptual Physics 12
Wrap a fur coat around a thermometer. Will its temperature rise?
Read more -
Chapter : Problem 44 Conceptual Physics 12
At what common temperature will a block of wood and a block of metal both feel neither hot nor cold to the touch?
Read more -
Chapter : Problem 43 Conceptual Physics 12
If \(70^{\circ} \mathrm{F}\) air feels warm and comfortable to us, why does swimming in \(70^{\circ} \mathrm{F}\) water feel cool? Text Transcription: 70^circ F
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Chapter : Problem 45 Conceptual Physics 12
If you hold one end of a piece of metal against a piece of ice, the end in your hand soon becomes cold. Does cold flow from the ice to your hand? Explain.
Read more -
Chapter : Problem 46 Conceptual Physics 12
Wood is a better insulator than glass, yet fiberglass is commonly used as an insulator in wooden buildings. Explain.
Read more -
Chapter : Problem 47 Conceptual Physics 12
Many tongues have been injured by licking a piece of metal on a very cold day. Why would no harm result if a clean piece of wood were licked on the same day?
Read more -
Chapter : Problem 48 Conceptual Physics 12
Visit a snow-covered cemetery and note that the snow does not slope upward against the gravestones. Instead, it forms depressions, as shown. Can you think of a reason for this?
Read more -
Chapter : Problem 49 Conceptual Physics 12
Why are mittens warmer than gloves on a cold day?
Read more -
Chapter : Problem 50 Conceptual Physics 12
Wood conducts heat very poorly—it has a very low conductivity. Does wood still have a low conductivity if it is hot? Could you quickly and safely grasp the wooden handle of a pan from a hot oven with your bare hand? Although the pan handle is hot, is much heat conducted from it to your hand if you grasp it briefly? Why would it be a poor idea to do the same with an iron handle? Explain.
Read more -
Chapter : Problem 51 Conceptual Physics 12
Does wood have a low conductivity if it is very hot—that is, in the stage of smoldering, red-hot coals? Could you safely walk across a bed of red-hot wooden coals with bare feet? Although the coals are hot, does much heat conduct from them to your feet if you step quickly? Could you do the same on red-hot iron coals? Explain. (Caution: Coals can stick to your feet, so—OUCH!— don’t try it!)
Read more -
Chapter : Problem 52 Conceptual Physics 12
Is it possible for heat to flow between two objects with the same internal energy? Can heat flow from an object with less internal energy to one with more internal energy? Defend your answers.
Read more -
Chapter : Problem 53 Conceptual Physics 12
When two cups of hot chocolate, one at \(50^{\circ} \mathrm{C}\) and the other at \(60^{\circ} \mathrm{C}\), are poured into a bowl, why will the temperature of the mixture be between \(50^{\circ} \mathrm{C}\) and \(60^{\circ} \mathrm{C}\)?
Read more -
Chapter : Problem 54 Conceptual Physics 12
Why is it incorrect to say that, when a hot object warms a cold object, temperature flows between them?
Read more -
Chapter : Problem 55 Conceptual Physics 12
Why is it incorrect to say that, when a hot object warms a cold one, the increase in temperature of the cold one is equal to the decrease in temperature of the hot one? When is this statement correct?
Read more -
Chapter : Problem 56 Conceptual Physics 12
In a mixture of hydrogen and oxygen gases at the same temperature, which molecules move faster? Why?
Read more -
Chapter : Problem 57 Conceptual Physics 12
One container is filled with argon gas and the other with krypton gas. If both gases have the same temperature, in which container are the atoms moving faster? Why?
Read more -
Chapter : Problem 58 Conceptual Physics 12
Which atoms, on average, move slower in a mixture: U-238 or U-235? How would this affect diffusion through a porous membrane of otherwise identical gases made from these isotopes?
Read more -
Chapter : Problem 59 Conceptual Physics 12
Solid uranium can be converted chemically to uranium fluoride, \(U F_{6}\), which can be cooked up into a dense vapor that diffuses through a porous barrier. Which is likely to diffuse at a greater rate: a gas with isotope U-235 or U-238? Text Transcription: UF_6
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Chapter : Problem 60 Conceptual Physics 12
Consider two equal-size rooms connected by an open door. One room is maintained at a higher temperature than the other one. Which room contains more air molecules?
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Chapter : Problem 61 Conceptual Physics 12
In a still room, smoke from a candle will sometimes rise only so far, not reaching the ceiling. Explain why
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Chapter : Problem 62 Conceptual Physics 12
Ice cubes float in a glass of iced tea. Why would cooling be less if the cubes were instead on the bottom of the drink?
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Chapter : Problem 63 Conceptual Physics 12
Release a single molecule in an evacuated region and it will fall as fast as, and no differently from, a baseball released in the same region. Explain.
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Chapter : Problem 65 Conceptual Physics 12
What does the high specific heat of water have to do with convection currents in the air at the seashore?
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Chapter : Problem 66 Conceptual Physics 12
If we warm a volume of air, it expands. Does it then follow that if we expand a volume of air, it warms? Explain.
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Chapter : Problem 67 Conceptual Physics 12
Ceiling fans can make you feel cooler in a warm room. Do ceiling fans reduce the room temperature?
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Chapter : Problem 68 Conceptual Physics 12
To save energy, some ceiling fans are reversible so that they drive air down or pull it up. In which direction should the fan drive the air during winter? In which direction during summer?
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Chapter : Problem 69 Conceptual Physics 12
A snow-making machine used for ski areas blows a mixture of compressed air and water through a nozzle. The temperature of the mixture may initially be well above the freezing temperature of water, yet crystals of snow are formed as the mixture is ejected from the nozzle. Explain how this happens.
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Chapter : Problem 70 Conceptual Physics 12
In which form of heat transfer is a medium not required?
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Chapter : Problem 71 Conceptual Physics 12
Why does a good emitter of heat radiation appear black at room temperature?
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Chapter : Problem 72 Conceptual Physics 12
Since energy is radiated by all objects, why can’t we see them in the dark?
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Chapter : Problem 73 Conceptual Physics 12
A number of bodies at different temperatures placed in a closed room share radiant energy and ultimately reach a common temperature. Would this thermal equilibrium be possible if good absorbers were poor emitters and poor absorbers were good emitters? Explain.
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Chapter : Problem 74 Conceptual Physics 12
From the rules that a good absorber of radiation is a good radiator and a good reflector is a poor absorber, state a rule that relates the reflecting and radiating properties of a surface.
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Chapter : Problem 77 Conceptual Physics 12
When there is morning frost on the grass in an open park, why is frost unlikely to be found on the ground directly beneath park benches?
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Chapter : Problem 76 Conceptual Physics 12
Even though metal is a good conductor, frost can be seen on parked cars in the early morning even when the air temperature is above freezing. Provide an explanation.
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Chapter : Problem 75 Conceptual Physics 12
The heat of volcanoes and natural hot springs comes from trace amounts of radioactive minerals in common rock in Earth’s interior. Why isn’t the same kind of rock at Earth’s surface warm to the touch?
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Chapter : Problem 78 Conceptual Physics 12
Why is whitewash sometimes applied to the glass of florists’ greenhouses in the summer?
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Chapter : Problem 79 Conceptual Physics 12
On a very cold sunny day, you wear a black coat and a transparent plastic coat. Which coat should be worn on the outside for maximum warmth?
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Chapter : Problem 80 Conceptual Physics 12
If the composition of the upper atmosphere were changed so that it permitted a greater amount of terrestrial radiation to escape, what effect would this have on Earth’s climate?
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Chapter : Problem 81 Conceptual Physics 12
Why is the insulation in an attic commonly thicker than the insulation in the walls of a house?
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Chapter : Problem 83 Conceptual Physics 12
Discuss the purpose of a layer of copper or aluminum on the bottoms of stainless steel cookware.
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Chapter : Problem 82 Conceptual Physics 12
Make up a multiple-choice question to test a classmate’s understanding of the distinction between conduction and convection. Write another question in which the term radiation is the correct answer.
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Chapter : Problem 84 Conceptual Physics 12
Discuss in terms of physics why restaurants serve baked potatoes wrapped in aluminum foil.
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Chapter : Problem 85 Conceptual Physics 12
If you were caught in freezing weather with only your own body heat as a source, discuss whether you’d be warmer in an Arctic igloo or in a wooden shack.
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Chapter : Problem 86 Conceptual Physics 12
A friend says that the molecules in a mixture of gas in thermal equilibrium have the same average kinetic energy. Do you agree or disagree? Explain.
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Chapter : Problem 87 Conceptual Physics 12
Your friend states that the average speed of all hydrogen and nitrogen molecules in a gas is the same. Do you agree or disagree, and why?
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Chapter : Problem 88 Conceptual Physics 12
Why wouldn’t you expect all the molecules of air in your room to have the same average speed? Relate your discussion to mass and kinetic energy.
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Chapter : Problem 89 Conceptual Physics 12
Soaring birds and glider pilots can remain aloft for hours without expending power. Discuss why this is so.
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Chapter : Problem 90 Conceptual Physics 12
Why does helium released into the atmosphere eventually disappear into space?
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Chapter : Problem 91 Conceptual Physics 12
Is it important to convert temperatures to the Kelvin scale when we use Newton’s law of cooling? Discuss why or why not.
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Chapter : Problem 92 Conceptual Physics 12
Suppose at a restaurant you are served coffee before you are ready to drink it. In order that it be hottest when you are ready for it, should you add cream to the coffee right away or wait until you are ready to drink it?
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Chapter : Problem 93 Conceptual Physics 12
If you wish to save fuel and you’re going to leave your warm house for half an hour or so on a very cold day, should you turn your thermostat down a few degrees, turn it off altogether, or let it remain at the room temperature you desire?
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Chapter : Problem 94 Conceptual Physics 12
If you wish to save fuel and you’re going to leave your cool house for half an hour or so on a very hot day, should you turn your air-conditioning thermostat up a bit, turn it off altogether, or let it remain at the room temperature you desire?
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Chapter : Problem 95 Conceptual Physics 12
As more energy from fossil fuels and other fuels is released on Earth, the overall temperature of Earth tends to rise. Discuss how temperature equilibrium explains why Earth’s temperature cannot rise indefinitely
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Chapter : Problem 96 Conceptual Physics 12
Discuss the function of a photovoltaic cell. What does it produce from what?
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Chapter : Problem 97 Conceptual Physics 12
Discuss why a \(1-\mathrm{ft}^{2}\) hole in a ceiling that admits sunlight when the Sun is overhead is like having a 100-W bulb in the room. Assume the atmosphere reduces solar energy at Earth’s surface as \(1.0 \quad \mathrm{kW} / \mathrm{m}^{2}\). Text Transcription: 1-ft^2 1.0 kW / m^2
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Chapter : Problem 99 Conceptual Physics 12
In what way did the Industrial Era contribute to climate change? Discuss better uses of fossil fuels than creating heat and smoke.
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Chapter : Problem 100 Conceptual Physics 12
Discuss the correlation between a growing human population and climate change.
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